Senior Bush administration officials sternly cautioned the 9/11 Commission against probing too deeply into the terrorist attacks of September 11, 2001, according to a document recently obtained by the ACLU.

The notification came in a letter dated January 6, 2004, addressed by Attorney General John Ashcroft, Defense Secretary Donald H. Rumsfeld and CIA Director George J. Tenet. The ACLU described it as a fax sent by David Addington, then-counsel to former vice president Dick Cheney.

In the message, the officials denied the bipartisan commission's request to question terrorist detainees, informing its two senior-most members that doing so would "cross" a "line" and obstruct the administration's ability to protect the nation.

If you've been paying attention, you know I've been poring through the 9/11 Report to figure out how useful the interrogation reports from the waterboarded detainees were, and when they made them.

That exercise shows that the 9/11 Report found just 10 pieces of intelligence from Abu Zubaydah's interrogation reports informative and credible; it found just 16 pieces of such intelligence in al-Nashiri's interrogation reports. And while the Commission did find KSM's interrogation reports to be incredibly useful, an incomplete index (I'm working on this, but it's on the back burner for the next week) of the references to KSM show that many of his most productive interrogation sessions came long after he was waterboarded. And, as Philip Zelikow made clear in a memo relating to the torture tape destruction, there were abundant other problems with the quality of the interrogation reports coming from CIA, too.